Bridge.



www0/awo mLm/LJMM- MWMQWW D. B. LUTEN.

BRIDGE.

APPLICATION FILED MAR. 8| 1909.

Patented J une A6, 1916.

Danie! B, Liften.

Hovnmd DANIEL B. LUTEN, OF INDIANAPOLIES, INDIANA BRIDGE.

Original application led November 1, 1906, Serial No. 341,605.

Specication of Letters Patent.

Patented June 6, 1916.

Divided and this application filed March 8,

1909. Serial No. 481,961.

To all whomy t may concern.'

Be it known that I, DANIEL B. LUTEN, a citizen of the United States,residing at indianapolis. in the county of Marion and State of Indiana,have invented certain new and useful Improvements in Bridges, of whichthe following is a specification.

My invention relates to concrete structures comprising bridges or archesin series balanced upon piers between the spans, and the object of myinvention is to so apply myv improved construction to bridges or otherarched structures that arches having unequal horizontal thrusts, or ofunequal iengths, may be balanced against each other upon the saine pier.

This application is plication tiled by me No. 341,605.

The accompanying drawings illustrate my invention.

Figure l is an elevation of a brldge constructed in' accordance with mypresentanvention; Fir. 2 is a longitudinal yertical section; an( Fig. 3a detail Showing the manner of balancing arches of difierent iengths.

lu a bridge consisting of several spans it is highly desirable for thesake of appearance, that the middle span should be the longest span; forotherwise, to one stand ing at one end of the structure, the nearestspan will appear the dominating span, due to an optical illusion, thusapparently destroying the symmetry and dignity of the structure.Moreover the main span in the middle of the structure makes betterp'rovision for floods. And with spans decreasing in length toward theabutments, the thrust on the abutment is decreased and the efiiciencyot' the structure thus doubly increased. The balancing oi unequal archspans upon their intermediate piers has hitherto been accomplished bygiving to the longer spans an increased rise, thus reducing the thrustof the longer span; but this can be of but limited application, for inorder to maintain a division of an ap- Nov. 1, i906, Serial the thrustsat a constant value, the increase in the rise must be made greaterproportionately, than the increase in span, and since a bridge floormust be made substantially level, no great variation oi' span can bepermitted. Moreover even a. slight variation of span results in aconsiderable elevation of the crown of the main span over those of theend spans. lf then the structure were to be submerged in iood to a pointnear the crowns of the short arches, the thrusts of the short arches'would be greatly reduced by the buoyancy of the Water and the mainarch, not yet submerged, would exercise a much greater thrust on thepier, tending to overturn it in the direction of the shorter submergedarch. My im proved construction enables me to balance arches of unequalspaii upon slender piers Without increasing the rise o the longer span.

As a means for balancing unequal arches upon the pier, I find itdesirable to arrange the arches as shown particularly in Fig. 1. Inorder to accomplish this result, instead of making the shorter spanHatter than the longer one, as has heretofore been the custom, thethrusts may be balanced by raising the end of the shorter span to meetthe pienI at a higher point than the longer spanas shown in detail inFig. Where the line of thrust E of the short span meets the line ofthrust D of the longer span, upon the` long span side of the centralpier, the force D however, being greater than the force E, the resultantF will be deflected to cross the center line of the pier and this line Fmay be made to emerge from the base of the pier Within the middle third,although, it' the pier be reinforced along its face as later described,this is not absolutely essential. It becomes immediately apparent thatby this means al level bridge Without camber may be readily produced, asillustrated in Fig. 1, Where the spans gradually increase in length, theadjacent end of each shorter span rising upon the adjacent end of thenext', fgllowing longer span. This inclination in the end 3112112 (lfthe SQI'QS Will alSO Save material in the abutmentat the end of thebridge, since it lowers the spriiglng llne, and this may be exaggeratedfor that purpose. For the salie of appearance the ap` parent springingsmay 'oe maintained at an actual level on the piers by distortion of thecurves, While the virtual springings are alternately elevated. Thismethod ofbalancing the arches provides for the equahzmgof the thrustsdue to the fixed load by the introduction ot a bending moment in thepier. Ifthe pier is very slender, so that the resultant F may passoutside of the middle third, I reinforce the pier against this moment byproviding reinforcing members 40,

reinforcing members may be, if desired, downward extensions fromreinforcing members 41 which extend through the arch either adjacent theintradosal or ythe extradosal surfaces being preferably extensions ofthe extradosal members.

Since the moving loads, on arches supported upon an intermediate pier,do not balance, their thrusts also will be unequal and are resisted bythe reinforcing members thus embedded near each face of the pier.

The super-elevation required in the shorter arch above the longer arch,may be determined by equating the moments of their respective thrusts attheir intersection with the center line of the pier, taken about thebase of the pier as a center.

I claim as my invention l. In combinati0n,'two arches of unequal span,and an intermediate pier upon wh'ich such arches meet, the pier being soslender that if either 'arch is removed the line of thrust due to theother arch on the pier emerges from the pier outside of the middle thirdof the pier base so that the pier is incapable of supporting one of saidarches 'with the other removed, the center line of the arch-rib of theshorter span meeting the center line of the pier at a point fartherremoved from the base of the pier than is the intersection of the centerline of the archrib of the longer span with the center line of the pier.

In combination, two arches of unequal span, and an intermediate pierupon which such arches meet, the pier being so slender that if eitherarch is removed the line of thrust due to the other arch on the pieremerges from the pier outside of the middle third of the pier base sothat the pier is incapable of supporting one of said arches with theother removed, and the outer surfaces of the two arches intersectingeach other on that side of the center line of the pier toward the longerspan.

3. The combination of a series of arches of span decreasing toward theend, each arch of shorter span having its two virtual springings atdierent heights and its higher virtual springing toward the adjacentarch of longer span and higher than the adjacent springing of saidadjacent arch of longer span.

. 4. The combination of a plurality of arches of unequal span, and apier supporting the adjacent ends of two such arches, that end of theshorter arch which is supported by said pier being elevated above thatend of the longer arch which is so supported and also above the otherend of the shorter arch.

5. The combination of a series of arches,

an intermediate arch of the series being longer than the two adjacentarches an having its two virtual springings atv substantially the sameheight, and each of said two adjacent arches having its two virtualspringings at different heights and its higher virtual springing towardthe intermediate arch and higher than the adjacent springing of saidintermediate arch.

YIn witness whereof, I have hereunto set my hand and seal atIndianapolis, Indiana, this fifth day of March, A. D. one thousand ninehundred and nine.

' DANIEL B. LUTEN. [11. 5.]

Witnesses:

C. H. KNIGHT, J. P. COOK.

(topics nt this patent may be obtained tor avc centi each, by addressingthe Commissioner ol Patenti,

Wilmington, n. c."

